kernel - Assert on remaining known races

* Add a flag to catch remaining known kevent races and assert on the case.

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index c3526d6..f859dae 100644 (file)
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -941,9 +941,16 @@ kqueue_scan(struct kqueue *kq, struct kevent *kevp, int count,
                 * WARNING!  We must leave KN_QUEUED set to prevent the
                 *           event from being KNOTE()d again while we
                 *           potentially block in the filter function.
+                *
+                *           This protects the knote from everything except
+                *           getting dropped.
+                *
+                * WARNING!  KN_PROCESSING is meant to handle any cases
+                *           that leaving KN_QUEUED set does not.
                 */
                TAILQ_REMOVE(&kq->kq_knpend, kn, kn_tqe);
                kq->kq_count--;
+               kn->kn_status |= KN_PROCESSING;
 
                /*
                 * Even though close/dup2 will clean out pending knotes this
@@ -958,7 +965,8 @@ kqueue_scan(struct kqueue *kq, struct kevent *kevp, int count,
                 */
                if ((kn->kn_fop->f_flags & FILTEROP_ISFD) &&
                    checkfdclosed(kq->kq_fdp, kn->kn_kevent.ident, kn->kn_fp)) {
-                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
+                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE |
+                                          KN_PROCESSING);
                        continue;
                }
 
@@ -968,7 +976,7 @@ kqueue_scan(struct kqueue *kq, struct kevent *kevp, int count,
                 * immediately triggered.
                 */
                if (kn->kn_status & KN_DISABLED) {
-                       kn->kn_status &= ~KN_QUEUED;
+                       kn->kn_status &= ~(KN_QUEUED | KN_PROCESSING);
                        continue;
                }
 
@@ -979,7 +987,8 @@ kqueue_scan(struct kqueue *kq, struct kevent *kevp, int count,
                 */
                if ((kn->kn_flags & EV_ONESHOT) == 0 &&
                    filter_event(kn, 0) == 0) {
-                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
+                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE |
+                                          KN_PROCESSING);
                        continue;
                }
 
@@ -991,15 +1000,17 @@ kqueue_scan(struct kqueue *kq, struct kevent *kevp, int count,
                 * Post-event action on the note
                 */
                if (kn->kn_flags & EV_ONESHOT) {
-                       kn->kn_status &= ~KN_QUEUED;
+                       kn->kn_status &= ~(KN_QUEUED | KN_PROCESSING);
                        knote_detach_and_drop(kn);
                } else if (kn->kn_flags & EV_CLEAR) {
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
-                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
+                       kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE |
+                                          KN_PROCESSING);
                } else {
                        TAILQ_INSERT_TAIL(&kq->kq_knpend, kn, kn_tqe);
                        kq->kq_count++;
+                       kn->kn_status &= ~KN_PROCESSING;
                }
        }
        TAILQ_REMOVE(&kq->kq_knpend, &local_marker, kn_tqe);
@@ -1321,6 +1332,7 @@ knote_dequeue(struct knote *kn)
        struct kqueue *kq = kn->kn_kq;
 
        KASSERT(kn->kn_status & KN_QUEUED, ("knote not queued"));
+       KKASSERT((kn->kn_status & KN_PROCESSING) == 0);
 
        TAILQ_REMOVE(&kq->kq_knpend, kn, kn_tqe);
        kn->kn_status &= ~KN_QUEUED;

diff --git a/sys/sys/event.h b/sys/sys/event.h
index 9a0d759..b568178 100644 (file)
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -196,6 +196,7 @@ struct knote {
 #define KN_DETACHED    0x08                    /* knote is detached */
 #define KN_CREATING    0x10                    /* creation in progress */
 #define KN_DELETING    0x20                    /* deletion in progress */
+#define KN_PROCESSING  0x40                    /* queued event processing */
 
 #define kn_id          kn_kevent.ident
 #define kn_filter      kn_kevent.filter